University of London Institute of Education, professor of educational psychology

University of London, professor of Psychology (appointed 1964)

University of Calgary, Alberta, Professor of Educational Psychology (appointed 1968)

Definition of Intelligence

“Intelligence A is the basic potentiality of the organism, whether animal or human, to learn and to adapt to its environment…Intelligence A is determined by the genes but is mediated mainly by the complexity and plasticity of the central nervous system…Intelligence B is the level of ability that a person actually shows in behavior—cleverness, the efficiency and complexity of perceptions, learning, thinking , and problem solving. This is not genetic…Rather, it is the product of the interplay between genetic potentiality and environmental stimulation…I have suggested that we should a third usage to Hebb’s Intelligence A and B, namely Intelligence C, which stands for the score or IQ obtained from a particular test (Vernon, 1979, pp. 10, 20).”

Major Contributions

Hierarchical group-factor theory of the structure of cognitive abilities

Author of 14 books and approximately 200 journal articles

Ideas & Interests

Philip Ewart Vernon’s contributions to the psychological literature were many and varied. His dissertation focused on the psychology of musical appreciation and auditory perception, but shortly after finishing his Ph.D. he began work with Harvard’s Gordon Allport on the study of expressive movement and the development of an instrument to measure personality-related values (Allport & Vernon, 1931; 1932). A revised edition of the Allport-Vernon Study of Values (SOV) is still widely used by psychologists more than 70 years after its initial publication (P. A. Vernon, 1994).

Vernon’s interest in personality research remained strong throughout his career, but his work in intelligence and giftedness gradually gained precedence. He was a proponent of Donald Hebb’s theory of intelligence, which divided human intellectual ability into two categories: He called the biological substrate of human cognitive ability “Intelligence A.” When Intelligence A interacts with environmental influences, Intelligence B is generated. Vernon elaborated this definition to include Intelligence C, which is what manifests on tests of cognitive ability—the score or IQ obtained on a particular test. These distinctions are important for the scientific study of intelligence, and they were adopted by other researchers including the German-born British psychologist Hans Eysenck. Both theorists noted that Intelligence B is essentially immeasurable due to the large number of confounding variables. Intelligence A is not a concrete “thing” that can be measured, and can only be approached through measures that yield an index of Intelligence C. Intelligence tests, however, are imperfect and vary to the degree that they reflect Intelligence A or B (Jensen, 1994).

Like many other prominent British intelligence theorists (e.g. Spearman and Burt), Vernon’s preferred research tool was factor analysis. In The Structure of Human Abilities (1950) Vernon presented his hierarchical group factor theory of the structure of human intellectual abilities. At the top of this hierarchy was Spearman’s general factor (g), which accounted for the largest source of the variance in intelligence. Below g were several major, minor and specific group factors. Because Vernon’s theory accounted for a general factor and group factors, it was seen as a reconciliation between Spearman’s two factor theory (which did not have group factors) and Thurstone’s multiple factor theory (which did not have a general factor.)

In subsequent years, Vernon became interested in studying the relative contributions of heredity and environment, and he summarized his conclusions in two books: Intelligence and Cultural Environment (1969) and Intelligence: Heredity and Environment (1979). Although he acknowledged the pivotal role of environmental factors, Vernon’s research led him to conclude that approximately 60% of the variance in human intellectual ability is attributable to genetic contributions. He extended this argument to implicate genes in the observed racial differences in intelligence test scores (P.A. Vernon, 1994). This controversial line of research was pursued in future years by Hans Eysenck and his student Arthur Jensen.

Selected Publications

Vernon, P. E. (1940). The measurement of abilities. London: University of London Press.